Several therapeutic and diagnostic applications in the medical field use ultrasonic energy. For example, ultrasonic energy can be used to enhance the delivery and/or effect of various therapeutic compounds. See, for example, U.S. Pat. Nos. 4,821,740, 4,953,565 and 5,007,438. In some applications, a catheter delivers ultrasonic energy and a therapeutic compound to a specific treatment site within the body. Such a catheter typically includes an ultrasonic assembly for generating the ultrasonic energy and a delivery lumen for delivering the therapeutic compound to the treatment site. Using this device, sometimes referred to as an “ultrasonic catheter,” the ultrasonic energy can be applied at the treatment site to enhance the therapeutic effect and/or the delivery of the therapeutic compound.
Ultrasonic catheters have successfully been used to treat human blood vessels that have become occluded or completely blocked by plaque, thrombi, emboli or other substances that reduce the blood carrying capacity of the vessel. See, for example, U.S. Pat. No. 6,001,069. To remove the blockage, solutions containing dissolution compounds can be delivered directly to the blockage site using an ultrasonic catheter. In this design, ultrasonic energy generated by the catheter enhances the delivery and/or therapeutic effect of the dissolution compounds.
Ultrasonic catheters can also be used to perform gene therapy on an isolated region of a body lumen. For example, as disclosed in U.S. Pat. No. 6,135,976, an ultrasonic catheter can be provided with one or more expandable sections for occluding a section of the body lumen. A gene therapy composition can then be delivered to the occluded section through a delivery lumen. Ultrasonic energy is then delivered to the occluded section to enhance the entry of the gene therapy composition into the cells of the occluded section.
Another use for an ultrasonic catheter is the delivery and activation of light activated drugs, as disclosed in U.S. Pat. No. 6,176,842. Additionally, ultrasound-enhanced thrombolytic therapy can be used to dissolve blood clots in arteries and veins in the treatment of conditions such as peripheral arterial occlusion and deep vein thrombosis. In such applications, an ultrasonic catheter delivers ultrasonic energy into a vessel, where the ultrasonic energy enhances thrombolysis with agents such as urokinase, tissue plasminogen activator (“TPA”) and others.